It is well known that ultraviolet rays generate active oxygen. When free radical type active oxygen among this active oxygen reacts with lipids or the like, a chain oxidation reaction is induced. Accordingly, free radicals cause enhanced damages to tissues.
Since skin is always exposed to oxygen and ultraviolet rays, it is one of the organs which are damaged by such stress from oxidization. In recent years, it has been considered that various types of active oxygen generated by ultraviolet rays causes peroxidation of sebum and lipids, denaturation of proteins, inhibition of enzymes and the like, thereby inducing inflammation of skin over the short term, and in addition, leading to aging, cancer and the like over the long term. Furthermore, it is believed that active oxygen and lipid peroxide are related to skin diseases such as atopic dermatitis, contact dermatitis and psoriasis. In this manner, active oxygen (free radicals) is deeply associated with skin aging and skin diseases.
Substances having an ability to capture free radicals can suppress and/or stop radical chain reaction. Accordingly, external preparations for skin using such antioxidants can be expected to be effective in preventing and/or improving skin aging (for example, spots, wrinkles and sagging) caused by stress from photo oxidation. In addition, they can also be expected to have preventive and/or improvement effects as external preparations for various skin diseases associated with free radicals.
Vitamins E and C are free radical capturing-type antioxidants in organisms. In addition, synthetic antioxidants, such as BHT and BHA, are also known.
However, the antioxidant ability (free radical capturing ability) of these substances cannot be said to be sufficient, and it is suspected that BHT and BHA are carcinogenic.
Accordingly, an antioxidant which has an excellent free radical capturing ability as well as high safety for skin has been desired.
Meanwhile, skin pigmentation, such as spots and freckles, is caused by excessive pigmentation of melanin due to hormonal abnormality or ultraviolet stimulation as a trigger, which enhances the melanin generation within pigment cells in epidermis.
For preventing such spots and freckles, a method by administrating or applying a substance which can suppress the melanin generation have conventionally been used. Specifically, it includes, for example, a method by administrating a large amount of L-ascorbic acid, a method by injecting glutathione or the like, and a method by locally applying kojic acid, cysteine, hydroquinone or the like, in such forms as ointments, creams, lotions.
At present, however, no substance satisfactory in effects, stability, safety and the like has been obtained.
As for natural anti-oxidants, extracts from Shiitake (Lentinus edodes), Enokitake (Flammulina velutipes), Shimeji (Lyophyllum decastes), Kawaratake (Coriolus versicolor), Matsutake (Tricholoma matsutake), Mannentake (Ganoderma lucidum), Hourokutake (Daedalea dickinsii), Nameko (Pholiota nameko) and other Basidiomycetes have been reported (Japanese Unexamined Patent Publication Nos. 5-317016, 6-65575, and 59-124984).
However, for extracts from Onnia orientalis, Astraeus hygrometricus or Pleurotus nebrodensis, no free radical capturing ability, antioxidative ability, melanin generation suppressive effect or application to external preparations for skin thereof has been known.
In addition, for extracts from Pleurotus abalones, although the platelet aggregation inhibition effect and rough skin improvement effect have been reported (Japanese Unexamined Patent Publication No. 2002-348247), no radical capturing ability, antioxidative ability or melanin generation suppressive effect thereof has been known.
Furthermore, for Pholiota squarrosa, although the production of a substance capable of degrading melanin by culturing mycelium thereof has been reported (Japanese Unexamined Patent Publication No. 2004-107284), no radical capturing ability, antioxidative ability or melanin generation suppressive effect thereof has been known.